Airplane stall and high-speed indicating apparatus



Dec. 28, 1943. R. D. LACOE 2,337,753

AIRPLANE STALL AND HIGH SPEED INDICATING APPARATUS Filed Feb. 24, 1941 INVENTOR. 204m Z). Lame- ATTORNEY.

I ing or other causes.

Peace... 28, 1943 UNITED STATES PATENT em e- AIRPLANE STALL AND HIGH-SPEED INDICATING APPARATUS Ralph D. Lacoe, San Diego, Calif. Application February 24, 1941, Serial No. 380,280 4 Claims. (01. 171-311) I My invention relates to a device for indicating a dangerous flyingcondition of an airplane, and can be used to deliver'an appropriate warning should flight become dangerous due to the approach or presence of a stalling condition, or due to a, condition of excessive speed. In the preferred embodiment tions of the presence of both of these dangerous flying conditions are given.

It is desirable to indicate the approach or presence of a maximum allowable speed for the airplane to avoid danger of such excessive speed as might cause structural failure through flutter- It is an object of my inven-.- tion to provide a device which can be used to indicate to the pilot the approach or presence of the maximum allowable speed. 1

It is known that if the angle of attack of .the airplane is increased to a predetermined point, a stalling condition ensues which destroys the lifting power of the wings. An increase in the angle of attach to 15 may often result in the production of such a dangerous stalling condition, and it is an object of the'present invention to provide a simple device which can warn the pilot of the approach or presence of such a dangerous stall: ing condition.

In accomplishing this result, I provide an air vane disposed in the air stream and which is asymmetrically pivoted about a generally horizontal axis so as to move up and down in response to changes in direction of the air stream. It is an object of the present invention to provide a novel mounting for such an air vane and a novel arrangement of electrical contacts which can'be used to give the desired warning.

It is another object of the invention to dispose such an air vane at such position with respect to the airplane as to be substantially out of themfiuence of the slip stream of the propeller, and

sufficiently removed from the air guiding surface 7 of the'airplane (for example; the fuselage and wings) so as not to be substantially influenced by the air streams adjacent to and affected by such surfaces during normal flight or under extreme variations in night conditions, such as side slips and skids. On the other features of the invention are novel irrespective of such mounting position of the device.

While in certain embodiments of the invention such an air vane may be pivotal axis, I have found that extremesensitivity and a toggle-like action with a more positive closing of the electrical contact can be ob-' tained by arranging the device so that the center hand, some of the positioned aft" of the of my invention, indicaa stream may the present invention to approach or presence of pressure of the air stream on the air vane is forward of the pivotal axis. While with such a system the vane can b made to assume a position generally parallel with the air stream, I prefer to disposethe air vane wardly inclined position so that the air stream normally exerts a downward pressure thereon, and to provide a suitable stop means tor limiting the motion of the air-vane under these downward pressures. If, then, the direction of the air stream changes (or what is in effect the same, the angle of attack of the airplane increases),v the air exert an upward pressure on the air vane to cause lifting thereof. It is an object of provide such and to arrange the vane in such position that a shift in pressure from the upper to the lower surfaces thereof will give an indication of a dangerous flying condition. It is another object of the'invention to restrict the angular move- 'ment of the-air vane about the pivotal axis so that a correction of the dangerous flying condition will move the vane member to its normal position and discontinue the warning signal. I Another'object of the invention is to provide a stall-responsive device in which the air vane is appropriately counter-balanced in such manner that the-force of gravity exerts'substantially no net moment tending to turn the air vane and its associated mechanism about the pivotal axis, and in such manner that jarring or vibration of the device. will not cause oscillation of the air vane.

Another object of the invention is to provide a device providing an air vane responsive to the of a stalling condition, in

conjunction with an auxiliary means controlling the warning signal. For example, the auxiliary means may comprise a device rendering the Waming or indicating means inoperative while the airplane is on the ground or before it has obtained a predetermined speed.

Another object 'of the inventionis to providea device including a stall-responsive air vane and an auxiliary air vane responsive tojthe velocity of the air stream, and to provide a novel operative connection between these air vanes, whereby, if desired, a si gle indicating means can give a warning of the approach or presence of either a stall condition or a condition of maximum allowable speed. 1

Another object of the invention is to provide an apparatus 'of this general class in which opposed spaced contacts are each arranged in operative shiftable relationship with an air vane.

Another object of the invention is to provide in a slightly 'downa system a novel operative connection: between a casing and ,one 'or more air vanes external thereof to provide a substantially dustproof and waterproof construction within which some of the operating mechanism is positioned.

Still another object of the invention is to-provide a pair of contacts which can be moved into signalling position in response to the approach or presence of a stalling condition and which can be moved into a signalling position in response to other conditions, such as the approach or presence of maximum allowable speed of the airplane. A further object of the invention is to provide means for retaining such contacts in non-signalling position under certain conditions for example, when the forward speed of the airplane is less than a predetermined amount, by which term I have reference not only to conditions during flight, but also to conditions when the airplane is at rest on the ground or moving along the ground preparatory tr. take-off.

Further objects and advantages of the invention will be made evident to those skilled in theart from the following description of the preferred embodiments of the invention.

Referring to the drawing:

Figure 1 is a fragmentary longitudinal sectional view of my airplane stall and high speed indicating apparatus taken from the line ll of Fig. 2 showing parts and portions in elevation to facilitate the illustration; Fig. 2 is a fragmentary sectional view taken from the line 2-2 of Fig. 1; Fig. 3 is a fragmentary longitudinal sectional view showing a modification of my airplane stall and high speed indicating apparatus taken from the lines 3-! of Fig. 4 showing portions broken away to facilitate the illustration; and Fig. 4 is a sectional view taken from the line 4-4 of Fig. 3.

Similar characters of reference refer to similar parts and portions'throughout the related views of the drawing:

member la, which tubular member la is arranged for use in connecting my airplane stall and high speed indicating apparatus to a portion of an airplane. For example, the tubular member In may extend downward from a wing of the airplane to position the device out of the slip stream ofthe propeller so as to be under the influence of the air stream moving relative to the plane and which. in eflect, is established by the forward motion of the airplane. This tubular member is is arranged to serve as a conduit for theelectrical conductors 4b and lb, which i are electrically connected-withthe electrical contacts 4 and I, shown best in Fig. l of the drawing. This casing I preferably consists of two casing portions lb andyic, which casing portions lb and lo are separable along the line Id. It 'will be observed by reference to-Fig. i of the drawing,

that these casing portions lb and Jc-aeparate at the axes of the air va'ne member I and the secondary air vane member I which are fournailed in opposite sides of said casing-member I,

as shown best in Fig. 2 of the The air vane member 2 is provided with a curved plate-like air vane portion assume to at its extended end with which are rigidly connected at' opposite sides thereof bifurcated portions 2b, which bifurcated portions 2b are rigidly secured at opposite ends of the iournalled shaft portion 2c of said air vane member 2, as

shown best in Fig. 2 of the drawing. Integral with this shaft portion 20 is a counterweight portion M, which extends backwardly from the shaft portion 2c near the upper inner side of the casing member I, as shown best in Fig. 1 of the drawing.

The counterweight portion 4d is illustrative of onefor'm ofcounterbalance means serving substantially .to counterbalance the gravitationally-induced moments about the shaft portion 2c under staticconditions, and to prevent vibration or oscillation of the air vane member 2 due to shocks or jars transmitted to the casing I, for example, when the airplane is moving on the ground. Rigidly connected with this counterweight portion 2d is an insulation contact en-' gaging member 2e, which is arranged to engage the shiftable end of the spring suppmt 4a of the electrical contact 4, as shown best in Fig.1

of the drawing. This spring support 4:: is

rigidly secured to the casing portion ic by means of the bolts Ia and this spring support 4a is insulated from the bolts le and the casing member l by the insulation members If. Secured to the casing portion lc in a similar manner by means of the bolts ie in spaced relation with the contact supporting spring support 411' are the electrical contact supportingspring Ia and the resilient :contact retaining member 8, as

shown best in Fig. 1 of the drawing.

.Referring particularly to Fig. l of the drawing. it will be observed that the electrical con-. tacts 4 and 5 are mounted'in opposed spaced 7 relation from each other on their respective spring supports 4a-and 5a and these contacts 4 and [are arranged to engage each other through the opening 60 in the resilient contact retaining member 8. Y 1

It will be noted that the resilient character of this contact retaining member 8 tends to force it toward the contact I and the extending end of this contact retaining member I is limited in its downward movement by engagement with the stop member 8b mounted in rigid connected relation with the casing member i, as shown best in Figs. 1 and 2 of the drawing. The contact-supporting spring to is also of resilient character but is 'formed of lighter material than the contact-retaining member 8 so that an upward 'forceapplied to the forward end of the former will first move'the contact 6 into the opening to, whereupon further upward movementwill cause the forward ends of both mem-' bers to move upward together. 7

The secondary air vane member 8' is constructed in substantially the same form as the air vanemember 2 providing a bifurcated portion retaininga secondary air vane. However, in this instance, the secondary air vane is disposed to face the air. stream to be responsive to the velocity of the air stream, or to the related forward motion of the airplane through the air. The secondary air vane member I is Journalled in opposite sides of the casing I, as shown best in Fig. 2-01 the drawing and'is provided with a shaft portion in similar to the shaft portion 2c of the air van'emember 2. Integral with this shaft portion In is an extending arm portion lb which is arranged to engage the lower 4 side of the contact supporting spring is to which the contact is electrically connected, as shown best in Fig. 1 of the drawing.

When the airplane is not in flight, the contact supporting spring 5a forces the arm portion 31) downwardly into engagement with the casin portion lc which serves asa stop. The armpor tion acts to counterbalance the external portions of the air Vane for example, an audible visible, or otherwise sen-.

sible signal, such indicating means being known in the' art, the details thereof being per se no part of the present invention. As will be hereinafter explained, the same indicating means can be used to give an indication of the approach or 4 and 5 are connected member 3 and, together with the contact supporting spring 5a, prevents oscillapresence of a stalling condition-orv of a high-speed condition, the pilot knowing which of these dangerous conditi ns exists due to his knowledge of the general conditions under which the airplane is flying. In general, the contact 4 is 'moved in response to conditions affecting the air vane 2a, while the contact 5 is moved in response to con-.

ditions affecting the secondary air vane 3. This secondary air vane 3 serves to maintain the con- 'tact 5 out of the locus of motion of the contact 4 when the airplane is on the ground and when the'forward motion of the airplane is small. In this connection, it will be apparent that the locus of motion of the contact 4, as well as of the counterweight portion 2d, is quite limited. The

'total angular motion of. the air vane member 2 about the axis provided by the shaft portion 20 is usually not more than 8 or 10 degreesv and. preferably, less than about 6 degrees in the embodiment shown. As viewed in Figure 1, the maximum counterclockwise motion of the air vane member 2 is determined by engagement between the counterweight portion 2d and the upper, inner surface of the casing portion lb. This is the normal position of the air vane member 2 during safe flying conditions. Clockwise rotation of the air vane member 2 is limited by engagement with one of the bolts Ie. During this clockwise rotation, the contact 4 will be-lowered. This will result in engagement with the contact range. In fact, flight in the lower portion of this range will not cause sufficient rearward pressure on the secondary air vane 3 to lift th contact retaining member 6 from stop 6b. However, upon the approach of a dangerous flying speed, the secondary air vane 3 will move rearward, due to increased pressure of the air stream,'until the contact retaining member 6 is raised fromthe stop 51) a sufiicient distance to permit engagement between the contact 5 and the contact 4, thus closing'the indicated circuit and giving a warning of the approach or. presence of' a dangerous over speed condition. Assoon as the pilot corrects thiscondition, the contact 5 will move downwardly from its engagement with the contact 4, thus interrupting the alarm. It is desirable that the secondary air vane 3 should move the contact 5 into the locus of motion of the contact 4 when the forward speed of the airplane is just below the stalling speed thereof.-

During normal flight, the air vane member 2 holds the air vane 2a in a position extending forwardly .in the air stream, but slightly depressed with respect thereto at such angle that the upper surface thereof is exposed to the air stream. A small downward force component is thus applied to the air vane 2a, downward motion of this air vane being prevented by the stop means comprising the upper surface of the counterweight portion 2d and the lower surface of the casing portion lb. Thus during normal flight, the contact 4 remains in its upper position, shown in Fig. 1. If the angle of attack of the airplane is increased to such a point that a stalling condition is imminent or present, the. relative position of the air vane 2a and the air stream changes to such an extent that the lower portion of this air vane is exposed to the air stream resulting in an upward pressure on the air vane portion 2a. As soon as this condition exists, the air vane portion 2a moves quickly upward until the counterweight portion 2d engages'the bolt le. This action is very rapid and is in the nature of a toggle action, moving the contact 4 downwardly and positively into electrical connection with the contact 5 and thus complet ng the indicating circuit, this circuit remaining closed until the stalling condition is corrected and until the air stream again strikes the upper surface of which time this air vane moves quickly downwardly to separate the contacts 4 and 5. The permissible angle of movement of the air vane member 2 is desirably made small so that a large 5 in-the event that this contact has been lifted into the opening to by the action of thesecondary air vane. On the other hand, if the airplane is on the ground and-the contact 5 has not been lifted, it will remain out of the locus of mo 5 into the opening 6a and thus into the locus of motion of contact 4. Assuming that the contact 4 is in its uppermost position, the contact 5 will never be lifted into electrical contact therewith so long as the flying speed is in a safe over correction of the stalling condition need not be made before the airvane 2a is again moved downwardly.

It is a feature of my invention that it can be designed to eliminate the giving of any warning of a stall condition until suchv a condition ac-- tually exists in flight. When the airplane first. starts moving on the ground preparatory to takeoff and with the tail structure in a low position,

the angle of attack is such that the air stream.

presses upwardly on the air vane 2a, thus lowering the contact 4. However, a warning will not be given at this time because the contact 5 re mains out of the locus of motion of the contact 4' due to the fact that sufilcient forward velocity has not been attained to move the air vane member 3 rearwardly. As soon as the tail is lifted,

the angle of attack changes to permit the air stream to press downwardly on the air vane 2a, thus retaining the contact 4 in its uppermost position. Subsequent slight lowering of the tail structure to permit take-oil is not suflicient to the air vane M, at

and give the desired warning.

In the modification, as shown in Figs. 3 and -4 of the drawing, the casing I is similar to the casing I, as hereinbefore described. The casing l is supported in connection with an airplane in substantially the same relation as the structure hereinbefore described by means of the tubular member 1a. This casing I consists of separable casing portions 1b and 1c which are to separate at the axis of the air vane member 8 and the secondary air vane member 8, as indicated by the line id in Fig. 3 of the drawing. Secured on the upper inner side of the casing portion lb in "spaced relation to each other are the electrical contacts Hi and II, as shown best in Fig. 3 of the.

drawing. These electrical contacts In and H are insulated from each other and the casing 1 by means .of insulation members 1e, as shown best in Fig. 3 of the drawing.

It will be here noted that the air .vane member 1 stalling condition in flight will lift the air vane 2a 8 is similar in construction and function to the air vane 20. of the structure hereinbefore described.

and the secondary air vane member 9 is similar to the secondary air vane {in structural arrangement and function, as shown best in Figs. 3 and 4 of the drawing. The air vane member '3 is provided with a shaft portion la and bifurcated arms-secured on the opposite ends'thereof designated 8b, asshownbest in'Fig. 4 of the drawing, these bifurcated arms carrying an air "vane similar to that indicated by the numeral 1a. Secured on the shaft portion In is a counterweight member By. The lower inner side of the casing portion 1c is arranged to be engaged. by the counterweight lg forming a stop for itsdownward movement and a stop member, In is provided to limit the upward movement of said counterweight 8g. Said stop'member 8h extends across the casing I, as shown best in Figs. 3 and 4. Integral with this counterweight 89 is an extending contact engaging portion which is arranged to. engage the upper side of the elec- "trical contact spring portion "a, as shown best in Fig. 3 of-the drawing. In opposed relation shown in Fig. 3 of the drawing. When the air-' I. respectively, as shown best in Fig. 3 of the drawing and these electrical conductor wires Ilb and ilb extend upwardly through the tubular member la, as shown best in Fig. '3 of the drawing. a I I The operation of the modified structure, as shownin Figs. Sand 4 of the drawing is substantially as follows: When this modified structure, as shown in- Figs. 3 and 4 o the drawing is secured on an airplane in flight, the secondary air vane 3 normally assumes the solid line position, as shown in Fig. 3 of the drawing. When the airplane approaches the maximum allowable speed, the secondary air vane member 3 is forced into dash line position A forcing the arm portion to into engagement with the upper end 'of the 'screw 3e shifting the counterweight member 30 airplane to which this modified structure is connected. It will be noted that the secondary air vane member 3 shifts from the dash line position C to the solid line position, as shown in Fig. 3 of the drawing. at a speed just below -the stalling speed of the airplane. 'I'herefore,'wheh the airplane approaches the stall. condition, the secondary air vane 8 is in the solid line position, as

vane 3 shifts to the dash line position B, the extended contact engaging portion lo thereof forces the contacts l0 and I i into engagement with each other indicating to the pilot of the airplane the stall condition of the airplane. It will be here noted that the tension spring M in connection with the counterweight 8c; of the, secondary air vane 9 is arranged in adjustable relation with the casing 1 by means of the adjusting screw 9e providing an arrangement whereby the secondary air vane 3 may be adjusted and arranged to operate at different speeds. The adjusting screw 3e, which is screw-threaded in the counterweight 3g is arranged to be adiusted in relation with the arm portion 9a of the air vane 3, as shown best in Fig. 3 of the drawing. When the secondary air vane 3 is in the dash line position 0, as shown in Fig. 3 of the drawing, the arm portion 0a thereof engages the arm portion 3d of the to the contact engaging portion lc is an arm opposed relation to an adjusting screw 3e which gaged by the extending arm portion 3a of the secondary air vane 3,as shown best in Fig.3 of

. portionld. This arm portion M is arranged in the drawing. This arm portion 3a is arranged in integral relation with the shaft 3b of the secondary air vane 3 and secured on this shaft id is a counterweight 00. all as shown best in Fig. 4 of the drawing. This counterweight 9c is positioned-in the casing 1 at one side of the counterweight lg of the air-vane 3. as shown best in 'Fig. 4 of the drawing. to the lower end of this counterweight 3c is a tension spring 0d.

the opposite'end of this tension spring It! is seecured to an adjusting screw 3e, all as shown best in Figs. 3 and 4 of the drawing. It wiii be noted' that the electrical contacts "and H are supported'on plate springs Ilia and Ha. as shown best in Figs..3 and 4 of the drawing. The electrical conductor wires ilb and it are electrically connected with the electrical contacts ii and counterweight 3g preventing the extending contact engaging portion 8c from forcing the contacts l0 and -l I into enga ement with each other.

This arrangement provides means whereby no signal may begiven'by the apparatus until the airplane has reached the approximate stalling speed. Therefore, when the airplane is on the ground and being maneuvered about, the signalling means in connection with the electricalwire conductor members lb and lib is inoperat ve.

. It will be apparent that, in both embodiments ofthe invention herein described in detail, I provide a pair of contacts movable from a non-signalling position to a signalling position upon the approach of a stall condition.

I believe it to .be new to mount an air vane asymmetric'allywith respect to an axis so that the center of pressure is. forward of the axis and to use this in indicatinga dangerous flying condi-.

tion, and it should be understood that, in certain embodiments of my invention. this feature can be'used irrespective. of its combination with auxiliary means responsive to the forward speedof the airplane. Likewise, I believe it to be new to' operative relation with said counterbalance poruse an air vane positioned in the air streamand movable about an axis, together with counterbalancing means serving substantially to coun- "of parts and portions and a certain modification,

I do not wish to be limited to this particular construction, combination and arrangement, nor to the modification. but desire to include in-the scope of my invention the construction, combination and arrangement and the modification substantially as set forth in the appended claims.

. Having thus described my invention, what I claim .as new and desire to secure by Letters Patout is:

1 In a combination airplane stall and high speed indicating apparatus of the class described, the combination of an enclosure casing, a stall indicating air vane member outwardly of said casing on a substantially horizontal plane with its pivotal axis in said casing and provided with a counterbalance portion positioned in said casing, a high speed indicating air vane outwardly of said casing on a substantially vertical plane with its pivotal axis in said casing and having an extended arm portion in said casing, a resiliently supported first contact member in said casing in operative relation with said counterbalance portion arranged in a, predetermined normal position when the airplane is in a safe fiying condition and is moved to a second position when the airplane is in a-stall condition, a resiliently supported second contact in said casing in operative relation with said extended arm portion arranged in normally spaccd relation from said first contact a distance greater than the range of movement or said first contact, said second resilientcontact being movable by said extended arm portion to engage the first resilient contact in said second position and in said normal position dependent upon the speed 01 the plane.

2. Ida combination airplane stall and high speed indicating apparatus of the class described, the combination oi an enclosure casing, a stallindicating air vane member outwardly 01- said casing on asubstantiallyhorizontal plane with its pivotal axis in-said casing and provided with o a counterbalance portion positioned in said cas-' ing, a high speed indicating air vane outwardly ;oi said casing on a substantially vertical plane with its pivotal axis in said casing and having an extended arm portion in said casing, a resiliently supported first contact member in said casing, in

tion arranged in a predetermined normal position whentheairplaneisinasaieflyingconditlonand is moved to a second position when the airplane is in a stall condition, a resiliently supported second contact in said casing in operative relation with said extended arm portion arranged in normally spaced relation from said first contact a distance greater than the range oi movement 7 said first contact, said second being movable by said extended arm portion to engage the first resilient contact in said second position and in said normal position dependent upon the speed 01 the plane, and stop means in cooperative relation with each of said vanes and the interior or said enclosure casing for ported sec their shiitable movements.

' 3. In a combination airplane stall and high speed indicating apparatus or the class described, the combination of an enclosure casing, a stall indicating air vane member. outwardly 01 said casing on a substantially horizontal plane with its pivotal axis in said casing and provided with a counterbalance portion positioned in said casing, a high speed indicating air vane outwardly of said casing on a substantially vertical plane with its pivotal axis in said casing and having an extended arm portion in-said casing, a resiliently supported first contact memberfin said casing in operative relation with said counter-balance portion arranged in a predetermined normal position when the airplane is in a safe flying condition and is moved to. a second position when the airplane is in a stall condition, a resiliently suprelation with saidextended-arm portion, arranged in normally spaced relation from said first contact a distance greater than the range of movement of said first contact, said second resilient contact being movable by said extended arm porfirst contact member by said extended arm portion. X

4. In a combination airplane stall and high speed indicating apparatus oi the class described, the combination of an enclosure casing, a stall indicating air vane member outwardly of said casing on asubstantially horizontal plane with its pivotal axis in said casing and provided with a counterbalance portion positioned ln-said casing, a high speed indicatingair vane outwardly 01 said casing on a substantially vertical planev with its pivotal axis in said casing and having a extended'arm portion in said casing, a resiliently supp rted first contact member in said casing in operative tion arranged in a predetermined normal posi tion when the airplane is in a safeflying condiresilient contact 1 tion andsis moved-to a second position when the airplane is in a stall condition, a resiliently sup- N portedsecond contact in said casing inoperative relation with said extended arm portion arranged in normally spaced relation from said first contact a distance greater than the range or movement or said first contact, said second resilient contact being movable by said extended arm portion to engage the first resilient contact in said second position and in said normal position dependentupon the speed of the plane, a third resilient member interposed between the resilient contact members provided vwith -an opening therein arranged to permit either or said contactmembers to pass through said intermediate resilient member, said third resilient member. being movable with said second contact toward said first contact-member by said extended arm por- ,tion, and stop means in said casing on one side or said third resilient member arranged to limit its movement in one direction. 7

A H oJ-IACOE."

0nd contact in said casing inoperative relation with said counterbalance por-u 

